You can buy lights anywhere, from a hardware store to local garden/nursery supply store or even a specialty hydroponics store, or of course online somewhere, like e-bay. You can use regular off the shelf fluorescent lights no problem. T5s and CFLs are better than lower lumen fluorescents. You could use about a 40-45 watt CFL rated at about 5000k to 6500k per square foot to have a pretty good setup. Even with Higher powered lights like metal halide or high pressure sodium, and you can find a real good 400watt digital kit on e-bay for around $100 USD, you can hang that light directly above the plants and supplement some side lighting with the fluorescent. There are a ton of different ways to set up your grow and it is mostly a personal preference. You do want most of your light and the most intense light shining from the top though. If you have space height limitations, you might want to look into training your plants to maintain a lower height of growth, also many many options there, from one plant trained to fill a screen at a certain height to growing numerous small plants and flower them early to keep height low.